The invention relates to a process of continuous electrolytic regeneration of aqueous ferric chloride solutions.
It is known that for etching fine structures in metal foils, ferric chloride solutions are used. The etching process is based upon the reaction EQU 2Fe.sup.3+ +Fe.fwdarw.3Fe.sup.2+ ( 1)
or EQU 2Fe.sup.3+ +Cu.fwdarw.Cu.sup.2+ +2Fe.sup.2+ ( 2)
In such an etching process, the ferric chloride solution becomes exhausted and results in a corresponding decrease in the etching speed; so that when the Fe.sup.3+ /Fe.sup.2+ ratio has reached a value of less than 3, it is necessary to either exchange the etching solution or regenerate it. There exists a known method of regeneration through the addition of chlorine to the solution which corresponds to the equation EQU Fe.sup.2+ +1/2Cl.sub.2 .fwdarw.Fe.sup.3+ +Cl.sup.- ( 3)
In such a process, the continuous addition of chlorine concentration gradually increases the iron chloride concentration so that the solution has to be diluted. The remittant excessive volume of the etching solution must be let out of the etching bath.
Among the disadvantages of the aforementioned process is the need for expensive safety precautions, in view of the chlorine manipulation, transport and storage, and the fact that the amount of etched-off iron gives rise to about a 7-times weight of iron chloride solution which constitutes a waste which is difficult to dispose of.
It is an object of the present invention to eliminate the drawbacks of the prior art as hereinabove referred to and to provide an improved process of continuous regeneration of ferric chloride solution.